1. Field of the Invention
The present invention relates to signal processing to remove or suppress undesired noise and, more particularly, to improving the quality of nuclear magnetic images.
2. Description of the Prior Art
Magnetic resonance imaging (MRI) has been gaining wider acceptance as a medical diagnostic tool to non-invasively prepare density maps of living tissue. The operation of magnetic resonance imaging is well known as indicated by the following two articles: "NMR Imaging In Medicine", Pykett, Scientific American 246/768 (May 1982), and "Nuclear Magnetic Resonance Imaging" Smith. Analytical Chemistry 57/595A (1985).
Within MRI equipment, a receiving antenna detects signals emitted from the patient and which are received as a sequence of complex time series from which images are produced. Unfortunately, the quality of the images can be greatly reduced by the reception and incorporation of noise generated in or about the receiving antenna. Such noise can be static or power surging in the electrical supply, strong local RF sources, such as radio/television transmitters and other adjacent, powerful medical equipment, or noise generated within the MRI itself. The reduction in image quality is evidenced by shadows, haze and/or bands of horizontal lines. Such reduction in image quality can present a problem to a medical practioner trying to correctly detect abnormal tissue within a patient.
To ensure that such noise is reduced or eliminated, the MRI is equipped with shielded/filtered power supply and a plurality of RF shields. Further, very careful attention is paid to proper manufacturing of components and proper maintenance. Due to continued use and the inherent complexity of the MRI, the undesirable effects of such received noise often becomes apparent. Usually, the MRI is then shut down until a repair person can adjust the RF shields, etc. to try to correct the problem. However, ceasing the use of the MRI is wasteful, and even the most skilled technician cannot remove noise caused by the MRI's internal components.
There is a need for a simple system that can be used on existing machines, as well as incorporated into the manufacture of an MRI to suppress or eliminate the undesirable effects of noise.